package ai.zixing.mashibing.basic_class.class06;

import java.util.ArrayList;

public class Code01_LinkedListMid {

    // head 头
    // 输入链表头节点，奇数长度返回中点，偶数长度返回上中点
    public static Node midOrUpMidNode(Node head) {
        // 没有节点|| 有一个节点|| 有连个节点
        if (head == null || head.next == null || head.next.next == null) {
            return head;
        }
        // 链表有3个或以上个节点
        Node slow = head.next;
        Node fast = head.next.next;
        while (fast.next != null && fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }

    // 输入链表头节点，奇数长度返回中点，偶数长度返回下中点
    public static Node midOrDownMidNode(Node head) {
        // 没有或者只有一个返回
        if (head == null || head.next == null) {
            return head;
        }
        // 有两个及两个以上
        Node slow = head.next;
        Node fast = head.next;
        while (fast.next != null && fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }

    // 输入链表头节点，奇数长度返回中点前一个，偶数长度返回上中点前一个
    public static Node midOrUpMidPreNode(Node head) {
        // 两个或两个一下节点，则返回空，中点的前一个为空
        if (head == null || head.next == null || head.next.next == null) {
            return null;
        }
        // 两个节点以上
        Node slow = head;
        Node fast = head.next.next;
        while (fast.next != null && fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }

    // 输入链表头节点，奇数长度返回中点前一个，偶数长度返回下中点前一个
    public static Node midOrDownMidPreNode(Node head) {
        // 为空或者只有一个节点则返回
        if (head == null || head.next == null) {
            return null;
        }
        // 只有两个节点
        if (head.next.next == null) {
            return head;
        }
        // 两个以上节点
        Node slow = head;
        Node fast = head.next.next;
        while (fast.next != null && fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }

    public static Node right1(Node head) {
        if (head == null) {
            return null;
        }
        Node cur = head;
        ArrayList<Node> arr = new ArrayList<>();
        while (cur != null) {
            arr.add(cur);
            cur = cur.next;
        }
        return arr.get((arr.size() - 1) / 2);
    }
    public static Node right2(Node head) {
        if (head == null) {
            return null;
        }
        Node cur = head;
        ArrayList<Node> arr = new ArrayList<>();
        while (cur != null) {
            arr.add(cur);
            cur = cur.next;
        }
        return arr.get(arr.size() / 2);
    }
    public static Node right3(Node head) {
        if (head == null) {
            return null;
        }
        Node cur = head;
        ArrayList<Node> arr = new ArrayList<>();
        while (cur != null) {
            arr.add(cur);
            cur = cur.next;
        }
        return arr.get((arr.size() - 3) / 2);
    }
    public static Node right4(Node head) {
        if (head == null) {
            return null;
        }
        Node cur = head;
        ArrayList<Node> arr = new ArrayList<>();
        while (cur != null) {
            arr.add(cur);
            cur = cur.next;
        }
        return arr.get((arr.size() - 2) / 2);
    }

    public static void main(String[] args) {
        Node test = null;
        test = new Node(0);
        test.next = new Node(1);
        test.next.next = new Node(2);
        test.next.next.next = new Node(3);
        test.next.next.next.next = new Node(4);
        test.next.next.next.next.next = new Node(5);
        test.next.next.next.next.next.next = new Node(6);
        test.next.next.next.next.next.next.next = new Node(7);
        test.next.next.next.next.next.next.next.next = new Node(8);

        Node ans1 = null;
        Node ans2 = null;

        ans1 = midOrUpMidNode(test);
        ans2 = right1(test);
        System.out.println(ans1 != null ? ans1.value : "无");
        System.out.println(ans2 != null ? ans2.value : "无");

        ans1 = midOrDownMidNode(test);
        ans2 = right2(test);
        System.out.println(ans1 != null ? ans1.value : "无");
        System.out.println(ans2 != null ? ans2.value : "无");

        ans1 = midOrUpMidPreNode(test);
        ans2 = right3(test);
        System.out.println(ans1 != null ? ans1.value : "无");
        System.out.println(ans2 != null ? ans2.value : "无");

        ans1 = midOrDownMidPreNode(test);
        ans2 = right4(test);
        System.out.println(ans1 != null ? ans1.value : "无");
        System.out.println(ans2 != null ? ans2.value : "无");
    }
}
